This invention relates generally to method and apparatus for detecting the extent of wear of a grinding wheel and to a method and apparatus for dressing a grinding wheel.
During operation of a known grinding machine, a grinding wheel is dressed at predetermined intervals during operation of the machine. Although the grinding wheel is rotated at a constant spindle speed during operation of the machine, the surface speed of the grinding wheel is higher when the grinding wheel is new and becomes less as the grinding wheel is worn away due to grinding and wheel dressing operations. When the wheel is new and has a higher surface speed, the rate of wear of the wheel is less than when the diameter of the wheel has been reduced. However, the wheel is dressed to the same extent when the wheel is new as when the wheel becomes worn and has a reduced diameter. In addition, the grinding wheel is commonly overdressed to compensate for the maximum rate of wheel wear which could possibly occur during grinding of a workpiece. This is done without regard for the actual extent of grinding wheel wear. Therefore, excessive material is removed from the grinding wheel during wheel dressing operations.
The removal of excessive material from a grinding wheel during wheel dressing increases the cost of a grinding operation due to the resultant wasting of grinding wheel material and due to the necessity of changing grinding wheels more often during the grinding of a large number of pieces. The changing of the grinding wheels can become particularly onerous when relatively high strength super alloys are being ground. This is because a relatively large volume of the wheel is consumed in order to remove a predetermined volume of material from a workpiece formed of a relatively high strength super alloy.
A probe member has previously been utilized to detect when an abrasive belt becomes worn. Thus, U.S. Pat. No. 3,691,698 discloses a probe or sensing member which is connected with a transducer to determine when an abrasive belt becomes worn. It should be noted that the probe member disclosed in this patent is maintained in continuous engagement with the belt during operation of the belt. This would result in the belt wearing away the probe.